This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. The yeast spindle pole body (SPB) is functionally equivalent to the centrosome in higher eukaryotic cells. The SPB is a multilayered organelle that organizes both the nuclear and cytoplasmic microtubules. We are working toward reconstitution of the microtubule nucleating activity of the SPB. The well characterized small gamma-tubulin complex contains three proteins: Tub4p, Spc97p, and Spc98p. We have expressed all three proteins in baculovirus and found that they readily assemble into a stable, soluble complex. However, the nucleation capacity of the small complex is quite low, suggesting we are missing components required for nucleation. The yeast spindle pole body (SPB) is functionally equivalent to the centrosome in higher eukaryotic cells. The SPB is a multilayered organelle that organizes both the nuclear and cytoplasmic microtubules. We are working toward reconstitution of the microtubule nucleating activity of the SPB. The well characterized small gamma-tubulin complex contains three proteins: Tub4p, Spc97p, and Spc98p. We have expressed all three proteins in baculovirus and found that they readily assemble into a stable, soluble complex. However, the nucleation capacity of the small complex is quite low. Recently the Agard lab (in collaboration with us) showed that the Tub4p molecules in the small complex are too far apart to nucleate microtubules.